Welding apparatus



July 20, 1965 T. H. COOPER ET A1. 3,196,248

WELDING APPARATUS Filed Nov. 2l, 1961 5 Sheets-Sheet l July 20, 1965 T.H. COOPER ET AL WELDING APPARATUS F'iled Nov. 2l, 1961 5 Sheets-Sheet 2Juy 20, 1965 Filed Nov. 2l, 1961 T. H. COOPER ET AL WELDING APPARATUS 5Sheets-Sheet 5 www Filed Nov. 2l, 1961 T. H. COOPER ET AL WELDINGAPPARATUS 5 Sheets-Sheet 4 y JAMES .7065/019 G/ July 2o, 1965 Filed Nov.21. 1961 T. H. cooPl-:R ETAL WELDING APPARATUS 5 Sheets-Sheet 5 UnitedStates Patent O 3,196,248 WELDING APPARATUS Thomas Henry Cooper,Laurence Kehle Hill, and .lames Joseph Giles, London, England, assignorsto BTR Industries Limited, London, England, a British company Filed Nov.21, 1961, Ser. No. 153,983 Claims priority, application Great Britain,Nov. 23, 196i), 40,309/ 60 3 Claims. (Cl. 219-125) The invention relatesto welding apparatus of the kind using an electric arc shielded by aninert gas such as argon and to a method of welding. It is an object ofthe invention to provide such apparatus and method which may be used toweld around a work-piece, for example to weld a seam, in a horizontalplane, between the end of a stainless steel p-ipe and an end iitting tobe attached to the pipe, or to weld a seam between two pipe lengths.

The invention provides a machine for use in welding around a work-pieceand comprising a non-rotating work holder, .a welding torch holder, asupport for the torch holder mounted for rotation around a workpieceheld by the work holder, conduits for supplying electricity and lashielding gas from a iixed (i.e., non-rotating) supply to the torch,said conduits each incorporating a sliding annular joint around the axisof rotation of the torch holder Iand permitting said rotation of theholder.

Such a machine is particularly suitable for welding stainless steel, butmay also be applied to titanium, tantalum, aluminium, bronze andbrasses.

Preferably the machine includes a conduit with a joint as aforesaid, forsupply of coolant (e.g., water) to the torch and there may also be areturn conduit for the coolant.

When there is a conduit for a coolant, as just described, the conduitfor the supply of electricity to the torch may comprise Ia cable withinthe coolant conduit, preferably a return conduit;

The joint in a conduit for the shielding gas or coolant liquid maycomprise in one joint part an' annular groove around the axis ofrotation with an opening into the groove and a port in the other jointpart opening into the groove, sealing means being provided on each sideof the groove.

The machine may also include a supply pipe for shielding gas leading toan outlet positioned to be within the work-piece (eg, in the region of aseam to be welded). The outlet orice may be composed of porous sinteredmaterial. The work holder may be tubular and the said supply pipe maypass through the holder.

One construction of the machin-e, described in more detail later,includes gas and electricity supplies, a motor for rotating the torchholder and means for effecting automatically, after a manual startingoperation, the following sequence of steps, first a purge by shieldinggas of the gas conduit or conduits, then starting of the torch rotation,then initiation of the arc followed by rotation of the torch holder fora predetermined time, termination of the arc with continued rotation fora further predetermined time of 'the torch and continued supply of gasand iinally stopping of the torch rotation and of the gas supply.

The invention also provides the method of welding together two tubularparts in end to end relation which comp-rires rotating an electricwelding torch around the outside of the joint to be welded for apredetermined time and at a constant speed, and supplying a shieldinggas to the weld region.

It is preferred to useas a filler for a weld seam, an integral part ofthe work, the part being suitably formed as later described.

A specitic construction of a welding apparatus according to theinvention will now be described, with reference to the accompanyingdrawings, in which:

FIGURE l is a perspective view of the apparatus,

FIGURE 2 is a sec'tional side view of the apparatus,

FIGURE 3 is a section on the line 3-3 of FIGURE 2,

FIGURE 4 is an enlarged sectional View on the line 4 4 in FIGURE 2,

FIGURE 5 shows the automatic timing circuit for the apparatus, and

FIGURE 6 is a View of a welding shield which fits around the joint to bewelded.

The welding apparatus in this example is designed -to weld a seambetween a bent pipe (c g., of stainless steel, aluminium, or titanium)and an end litting or union member to be attached to the pipe or to weldtwo such pipes together. A general view of the apparatus is shown inFIGURE 1.

The operating parts of the welding apparatus are all mounted on a stand10 which supports a rectangular box 9 having a table top` 11 supportinga cylindrical housing 12 sur-rounded by a guard 14. At the end ofthe boxadjacent the guard there is a work supp-ort pillar 13.

'Fitting into a central bore in the housing and continuing through ahole in the table top there is the stern 15 of a rotatable torch holderwhich ha-s a circular top plate 16 attached to the t-op of the stern.The stern 15 of the torch holder is mounted in a thrust race 17 at thebase of the housing and has a bearing sleeve and which works in a bush18 at the top of the housing. The upper bearing is lubricated through agrease passageway 19. The stern 15 of the torch holder projects belowthe table top and a gear wheel 20 is mounted on the projection soformed. 'Ilhe gear wheel 20 and hence the torch holder is driven by amotor 21 through a slip clutch, a gearbox 24 and a driving gear 23 allof which are housed in the box 9.

Internally concentric within the hollow stem 15 of the torch holder andprojecting through a central hole in the top plate of the torch holderthere is a tubular nonrotating work-holding column 26 to which the workis held by a chuck 27 fastened to the top end of the column. The column26 is mounted at its upper end in an annular bush 28 tted to the topplate of the torch holder and at its lower end in a bearing 30 fixed tothe stand and beneath the table top.

The work-holding column 26 is axially slidable in its bearings andmovement is etiected by turning a handwheel 28 which drives a chain 25connected to a cog 31 fixed to a nut 32. The nut 32 is held axially inthe lower mounting 30 of the work holding column and is threaded ontothe work holding column which is held against rotaf tion by bolts 29entering a keyway in the side of the column. column.

A pipe fitting 35., to be welded is held in position by the chuck 27 atthe top of the work holding column and a pipe 34, which enters into asocket 33 in the fitting 35, as shown in FIGURE 4, is supported by aclamp on a support arm 38 and a work centraliser on a support arm 37which arms are adjustably mounted on the work support pillar 13.Alternatively the arm 37 may be mounted on thetop plate 16. The workcentraliser 36 comprises a clamp held in a universal joint in the arm37.

The work support pillar 13 comprises a central rodshaped member 40 whichis held in a hollow cylindrical base member 42 which is fixed to the box9.

The welding torch 44 (which is a conventional water cooled argon arcwelding torch) is mounted on a pillar 43 on the top plate 16 of thetorch holder. This mounting is arranged so that a tine adjustment may beeffected to the torch in a vertical and/or horizontal plane.

There may be an additional pillar on the top plate 16 and carrying awelding shield which tits around the Rotation of the nut 32 raises andlowers the joint to be welded. This shield is shown diagrammatically inFIGURE 6 and comprises a horseshoe-shaped body 9i? which fits around thejoint. There is a channel 91 around the inside of the body and an argonsupply pipe 92 leading lto the channel. The mouth of the channel iscurved by a line mesh gauge. The welding torch has access to the jointbetween the arms of the horseshoe. There would be a series of differentdiameter shields to fit pipes to be welded of different diameter.

The supply of argon andl cooling water to the torch (and the weldingshield if used) will now be described.

There are three supply pipes leading to the housing from externalsources: an argon supply pipe d, arwater supply pipe 51, and a waterreturn pipe 52.\ The body member l2 is divided horizontally into vthreesections 55, 56S, 57 and the three supplyrpipes are each joined to Y theside of one of these sections by a union. The arrangement of the supplypipes is in the order, reading from top to bottom of the housing, ofargon supply 50, water supply 5l and water return 52.

From each union a horizontal bore 60 in the housing leads through to anannular groove 6l in the inner circumference of the housing and adjacentto the rotatable torch-holder 15. Around the edges of each annulargroove there are springeloaded rubber seals 63 which seal the housing tothe sleeve.

Each supply is connected between its annular groove 6l and the weldingtorch 44 by a throughway 65 connecting a port 66, in the stem l5 of thetorch-holder and which stem is open to the annular groove with a banjounion 6'7 mounted in the top-plate and connected by a pipe to the torch.Only one set of connections is seen in FIGURE 4 as the throughways 65are located around the circumference of the torch holder.

Each of the rubber seals 63 has two annular lips '72 which bear on thestem l5 and is lubricated through a nipple 73 in the top plate i6 of thetorch holder which leads through a drilling 75 in the stem to an opening7 6 between the lips of the seal.

The supply of electricity to the torch will now be described.

There is a `lower ring 58 of insulating material supported on the upperportion 55 of the housing and this lower ring 58 carries a spring loadedbrush 59 connected to the welding supply for the torch (which will bedescribed later).

There is an upper ring 77 of insulating material bolted to. theunderside of the top plate 16 which upper ring rotates with the topplate. The upper ring carries a slip ring 7S which co-operates with thebrush 59 on the lower ring 53. The slipring is connected through aconnection v 79 and an electrical lead to the torch. Dirt and dust areexcluded from the connection '79 by a cover plate 16a on the top plate16.

There is a mounting bracket lith on the table top 1l and this bracketcarries a microswitch assembly :fitti which is operated by a cam T02 onthe rotating table i6. Y There is a further supply of shielding gases (amixture of argon'with up to 2% nitrogen, helium or hydrogen) through ailexible pipe Sti in the bore of the work holding column which isfastened to a tubular metal endpiece Si screwed into a threaded hole S3at the centre of a plate 82 screwed into the column 26. An adaptor 84 isscrewed into the hole 83 from above the plate S2. The adaptor is in theform of a tube which is closed at its upper end, which slides inside theendy fitting and pipe to be welded, and has small outlet holes 85 forthe shielding gas above and below the seam to be welded. Alternativelythe adaptor may terminate in a plug of sintered material adjacent theseam through which material the gas is diffused. There will be a set ofsuch adaptors with diiferent lengths and diameters for different endfittings and pipes. Where the shape of the work-piece does not allow forthe insertion of any such adaptor, the adaptor is omitted, allowing forof shielding gas.

The fitting 35 to be welded to the pipe 34 has a socket 33 into whichthe end of the pipe is fitted and has, integral with and around thesocket mouth, an external projection or rib 86 of metal to provide aweld lilling. The rib of which the greater part is originally above theactual joint, may be of rectangular section or as shown, the externalcircumferential face may taper awayrfrorn the tube (i.e., downwardiy, sothat the lower diameter is smaller than the upper) because welding takesplace with the seam horizontal and the fitting below the pipe. Thus thefiller metal will tend to run downwards when molten and provide auniform thickness of weld. y

The torch is supplied from an ACR 150 welding unit (made by thel BritishOxygen Company Limited) which embodies a conventional tungsten inert gasrectifier and controls for the electrical supply and gas rflow to thetorch.

The ACR 150 welding unit supplies 70 v. to the arc and the arc strikeswhen a high frequency'supply is superimposed on'the 70 v. When the arcstrikes the voltage across the arc drops to about l() v.

The Ywelding time is governed by a timer which forms part of the circuitof FIGURE 5 which will be described later.

When the Vwelding operation stops, the welding unit carries out thefollowing sequence while the torch holder is still rotating: Y

(l) A crater filler comes period.

(2) The crater iiller stops and a gas delay timer cornes into operationso that the weid is still surrounded by shielding gas for a period.

(3) The gas supply is switched olf.

The sequence of operation of the apparatus will now lbe described.

First of all an adaptor 84 is screwed into place and the pipe andfitting to be welded together are clamped into place using the chuck 27,the work centraliser 26 and the clamp on the support arm 38.

The welding sequence is carriedout in conjunction with the ACR 150 by anautomatic control unit the essential parts of which are shown in FIGURE5.

vThe water supply is turned on and the welding unit is switched on. Theclosing of SW1 by the operator supplies 250 v. A.C. to transformer T1which supplies 6.3 v. to the heater of a pentode valve V.

On depressing a push button PBll a relay RLZ, which `is fed fromtransformer Til, is energised (since contacts RLS/3 are closed whenthere is no current in relay RLS) and relay RL2 closes conta-cts RL2/l,RLZ/Z and Ri/3. The energising current for relay RL2 is now suppliedthrough contacts RLZ/l and on the release of the push buttonPBl` by theoperator the relay RLZ is self-holding.

Contacts RLfZ/Z supply current to the bulb Bll which lights indicatingthat the control sequence has started.

Contacts RLZ/3 close the circuit to ythe contacts in the ACR 150 which:

(i) operates a solenoid opening a cock to supply shielding gas totheelectric arc T (and the welding shield if used) (ii) supplies 70 v. toRLli and the arc T (iii) initiates (but does not complete the circuitto) the high frequency arc-starting supply to the arc T.

A smal-l percentage of shielding gas by-passes the torch and ope-rates alpressure switch PS1 thus energising transformers T2 and T3. A solenoidS01 is energised by a Q5 v. tapping from transformer T2 and the solenoidoperates a valve 'to supply shielding gas to the flexible pipe Sti inthe work holding column and hence to the adaptor and the workpiece. Y Y

A 50 v. tapping on transformer T2 is rectied by a bridge rectifier REClland commences to charge capacitor C1 via a variable resistance VR]`(contacts RLT/l free ow into operation for a timed are normally closed).When Cl is charged (the time delay being varia-ble by altering the valueof resistance VRT) relay RLT is energised closing contacts RLl/S andRLT/2. The closing of contacts RLT/3 opens contacts RLll/ 1.

Contacts RLT/2 complete the circuit to the electric motor 2i to startthe motor and set the torch holder rotating. Thus the time during whichthe system is purged by the gas before the torch holder moves iscontrolled by the time taken to charge the capacitor C1 (the purge timeis usually about 30 seconds).

Contacts RTA/l of relay RIA are normally closed but relay RL4 is in the70 v. circuit of the ACR 150 to the arc and is energised to opcncontacts Rift/1 when contacts Ri/3 are closed. As this action is almostsimultaneous with the closing of pressure switch PSL no power issupplied from transformer T3.

When the torch holder and top plate have rotated to a predeterminedposition the cam operated microswitch assembly itil on the tablecompletes the HF supply circuit from t-he ACR 150 to the Welding arc.When the arc strikes the voltage across the torch and hence across therelay RIA drops from 70 v. to about l() v. closing contacts RIA/1 andcompleting the circuit from transformer T3 to the weld timing circuitwhich will -noW be described.

`Current is provided to the capacitor C3 from a potential dividernetwork consisting of a resistance R2 and two variable resistances VRZand VR3 in parallel with a smoothing capacitor C2 and in series with arectifier RECZ. The current reaches capacitor C3 through a resistance R3and a variable resistance VR4. When the voltage across C3 has risen toapproximately 150 v. the voltage regulator tube N strikes introducing anegative grid bias to the control grid of the valve V. The Valve Vconducts and energises a relay RLS opening contacts RLS/3 and closingcontacts RL3/1 and RLS/2. As voltage is now supplied to RLS directlythrough resistance R6 and contacts RL3/1, relay RLS becomes selfholding,while contacts RL3/2 short out capacitor C3 through resistance R4.

The opening of contacts RLS/3 de-energises the relay RL?. thus openingcontacts RLZ/, RLZ/Z and ELE/3. The opening of contacts RL2/3 initiatesthe following sequence in the ACR 15() (the torch holder continues torotate as contacts RLl/Z are still closed):

(i) the crater filler comes into operation for a preset period,

(ii) the crater filler stops and a shielding gas delay circuit comes4into operation for a preset period,

(iii) the shielding gas supply is cut off.

The fall in pressure when the shielding gas ceases to flow opens theswitch PS1, de-energising the transformers T2 and T3. Thus the contactsRLl/Z are opened stopping the electric motor Z1.

The operation is now completed as all the contacts revert to theirnormal positions until switch PBI is again depressed prior to the nextwelding operation.

It will be appreciated that the angle through which the torch turnswhile the weld is actually taking place is variable by alternative ofthe time taken to charge the capacitor C3 (i.e., by changing the valuesof the two d variable resistances VRR land V24.) The torch will usuallyturn through just more than 720.

rFhere are three controls in the apparatus which must be preset beforewelding commences. These arc:

(1) The motor speed by altering the resistance of the motor armaturecircuit.)

('2) The argon purge time (by altering VRll).

(3) The welding time (by altering VRA or VRE).

The important advantage of an automatic welding operation lis that oncethe three above controls have been preset, the machine will produce anydesired number of identical weld-s. This consistency and reliabilitycannot be produced even by a very experience manual Welder.

The chuck may be spring loaded so that an axial load may be applied tothe work-pieces during the operation of 'the apparatus.

We claim:

l.. A machine for welding around the outside of an clon gated `work-piece comprising (a) a non-rotatable housing with a central bore (b) atorch support having a tubular stem mounted lfor rota-ting coaxiallywithin the bore of the housing (c) means for etfecting rotation of thesupport (d) a non-rotatable tubular Work holder mounted coaXially withinthe stern of the torch support (e) means on the work holder for holdingan elongated workpiece coaxially with the holder (f) means on the torchsupport for mounting a welding torch for rotation on the support aboutthe work holder (g) the torch support having conduits and wires forfeeding shielding gas, coolant liquid and welding current respectivelyto a torch (h) the housing having conduits and wires for supplyingcoolant liquid, shielding gas and welding current respectively and (i)sliding annular joints between the housing and the torch supportconnecting the conduits and wires in the housing with the correspondingconduits and wires in the torch support, while permitting rotation ofthe torch support.

2. A lWelding machine as claimed in claim 1 and including means forholding a second workpiece adjacent the said elongated workpiece forwelding thereto.

3. A welding machine as claimed in claim 1 in which the tubular Workholder is mounted for axial adjustment within the stem of the torchsupport.

References Cited bythe Examiner UNITED STATES PATENTS 2,721,248 10/55Kirkpatrick 219-125 2,777,937 1/57 Bryant 219-125 2,817,745 12/57 Piliaet al. 2l9-125 2,844,707 7/58 Mrazzagatti 219-74 2,906,852 9/59 Cornellet al. 219-61 2,996,600 8/61 Gardner et al. 219-61 3,068,343 12/62Rossner 219-60 3,084,243 4/63 Gotch 219-60 3,134,894 5/64 Farnsworth219-125 RICHARD M. WOOD, Primary Examiner. JOSEPH V. TRUHE, Examiner.

1. A MACHINE FOR WELDING AROUND THE OUTSIDE OF AN ELONGATED WORKPIECECOMPRISING (A) A NON-ROTATABLE HOUSING WITH A CENTRAL BORE (B) A TORCHSUPPORT HAVING A TUBULAR STEM MOUNTED FOR ROTATING COAXIALLY WITHIN THEBORE OF THE HOUSING (C) MEANS FOR EFFECTING ROTATION OF THE SUPPORT (D)S NON-ROTATABLY TUBULAR WORK HOLDER MOUNTED COXIALLY WITHIN THE STEM OFTHE TORCH SUPPORT (E) MEANS ON THE WORK HOLDER FOR HOLDING AN ELONGATEDWORKPIECE COXIALLY WITH HOLDER (F) MEANS ON THE TORCH SUPPORT FORMOUNTING A WELDING TORCH FOR ROTATION ON THE SUPPORT ABOUT THE WORKHOLDER (G) THE TORCH SUPPORT HAVING CONDUITS AND WIRES FOR FEEDINGSHIELDING GAS, COOLANT LIQUID AND WELDING CURRENT RESPECTIVELY TO ATORCH (H) THE HOUSING HAVING CONDUITS AND WIRES FOR SUPPLYING COOLANTLIQUID, SHIELDING GAS AND WELDING CURRENT RESPECTIVELY AND (I) SLIDINGANNULAR JOINTS BETWEEN THE HOUSING AND THE TORCH SUPPORT CONNECTING THECONDUITS AND WIRES IN THE HOUSING WITH THE CORRESPONDING CONDUITS ANDWIRES IN THE TORCH SUPPORT, WHILE PERMITTING ROTATION OF THE TORCHSUPPORT.